Technical Field
Certain embodiments of the present invention relate to a regenerator which accumulates cooling generated by Simon expansion of a high pressure refrigerant gas supplied from a compression apparatus, and a regenerative refrigerator including the regenerator.
Description of Related Art
In some displacer type regenerative refrigerators, a displacer reciprocates in an inner portion of a cylinder, and thus, a refrigerant gas in an expansion space is expanded and cooling is generated. Moreover, in a pulse tube type regenerative refrigerator, a gas piston reciprocates in a pulse tube, and thus, a refrigerant gas in an expansion space is expanded and cooling is generated. The cooling of the refrigerant gas generated in the expansion space is accumulated in the regenerator, and cools a cooling object connected to the cooling stage. In addition, for example, as the refrigerant gas, helium gas is used.
A regenerator material is used in the regenerator. For example, in a cryogenic temperature region of 10 K or less, specific heat of a regenerator material made of a nonmagnetic material such as copper is lower than that of the helium gas which is the refrigerant gas. Accordingly, in the regenerator in the cryogenic temperature region, a regenerator material made of a magnetic material having higher specific heat in the temperature region is used.